Mitigation of the potential alkali–silica reaction of FNS using ground FNS as a supplementary binder

Alkali–silica reactivity of granulated ferronickel slag (FNS) aggregate was evaluated by accelerated mortar bar tests. The test results showed noticeable expansions of the samples containing 50% FNS aggregate due to potential alkali–silica reaction (ASR). On the other hand, finely ground FNS (GFNS) exhibited pozzolanic property in the studies of compressive strength development, thermogravimetric analysis and X-ray diffraction analysis. Therefore, GFNS was used as a partial replacement of cement to study its effect on the reduction of ASR. It was found that the use of GFNS for at least 30% cement replacement reduced the 10 d and 21 d mortar bar expansions below the allowable limits. The consumption of portlandite by the pozzolanic reaction of GFNS is considered as the primary reason for the reduction of expansion. The ASR mitigation process of GFNS was further confirmed by scanning electron microscopy images and energy-dispersive X-ray spectroscopy of the reaction product.